Sequencer Strip Addon
When rendering, you can specify that Blender saves in an image format like .png.

As long as you have set a render range (default is 250 frames), you can press the "Animation" button in the Scene properties>Render tab, Blender will generate a frame sequence in the path you set in the Scene properties>Output tab.



Notice that the button labelled "File Extensions" is ticked? That tells Blender to add the frame number to every rendered frame. This will keep your frame sequence in order when you load it into the VSE later.